This invention relates to a clinical electrothermometer for electronically detecting and digitally displaying a body temperature which is sized substantially equal to flat type clinical thermometers and has a waterproof casing structure.
A typical clinical electrothermometer comprises a temperature-sensing element for converting temperature information into electric signals, computing and display means for converting the electric signals into digital signals, computing the signals, and displaying the determined temperature, and a battery for supplying a power to these components. All the elements are housed in an elongated casing. A recent technical advance in the miniaturization of LSI's and other electronic circuit elements allows clinical electrothermometers to be manufactured in small size.
When such clinical electrothermometers are used in a hospital, infections among patients by way of a clinical electrothermometer must be prevented. For this purpose, the outer surface of the clinical electrothermometer is subjected to disinfection as by cleaning and rinsing. Most conventional electrothermometers, however, have a structure unsuitable for such disinfection.
In this type of clinical electrothermometer, a transparent display window must be provided in the casing which houses the computing and display means therein so that the temperature display may be viewed from the exterior. To this end, the casing is formed with an opening, which constitutes an obstacle in providing a waterproof structure.
A transparent window member may be fitted in an opening in the casing with adhesive to provide an adhesive seal for attaining a waterproof structure. However, such electrothermometers are difficult to mass produce in a consistent manner.
A transparent window member may also be secured to an opening in the casing by means of a packing and a screw. In this case, more parts are used to constitute the casing. Such a complicated structure is a bar against mass productivity as well as miniaturization.
Clinical electrothermometers of battery-replacing type have similar problems as mentioned above. A cover to be removably mounted for battery replacement is less waterproof at its mount and difficult to mass produce in a consistent manner.
To impart waterproofness to clinical electrothermometers, waterproof coatings may be applied onto the display window and cover portions. Such coatings must be transparent so as not to damage the function and appearance of the display window. A coating layer of transparent resin over the window portion may impart a sufficient waterproofness to the clinical electrothermometer, and the response of the probe to temperature is not retarded when a thin coating layer is employed.
However, heat must be applied in a drying step for the removal of the solvent when such a transparent resin is applied on the window portion in a usual manner. Conventional electrothermometers are heat resistant only up to about 60.degree. C. in consideration of the protection of electronic elements. Thus heat drying can not be employed in the manufacture of electrothermometers.
Resins capable of drying at relatively low temperatures such as ultraviolet-curable resins may be employed for the coating layer. However, there still remains a risk that electronic elements housed in the casing could be destroyed by heat from an ultraviolet lamp.
Room temperature vulcanizable silicone resins and rubbers may also be employed, but they take a long time until cured.
Since thermometers are often rubbed on the outer surface, for example, during cleansing, ordinary resins are insufficient in film strength and bond strength.
There are known few clinical electrothermometers which include a temperature-sensing element and display means combined and have a small-sized waterproof casing structure.
Japanese Utility Model Application Kokai No. 59-87639 discloses a clinical electrothermometer in which waterproofness is contrived by placing an O-ring of a synthetic rubber at the joint between the transparent window member and the opaque cylindrical casing. However, when such electrothermometers are mass produced, O-rings are often moved out of place allowing water and disinfectants to penetrate.